Right crank arm assembly for a bicycle and crank arm and front sprocket

ABSTRACT

A right crank arm assembly for a bicycle, comprises a right crank arm and at least one front sprocket coupled with the crank arm at least one coupling portion of the crank arm. The front sprocket has an inner side adapted, in use, to face towards the frame of the bicycle and an outer side opposite the inner side. The assembly comprises at least one first crank arm element which acts in contact with the front sprocket on one of said sides and at least one second crank arm element which acts in contact with the front sprocket on the other of said sides. The contact action of the crank arm elements on the two opposite sides of the front sprocket prevents the twisting deformation of the front sprocket during pedaling. Such a deformation would cause a reduction in the transmission efficiency of the right crank arm assembly.

FIELD OF INVENTION

The present invention relates to a right crank arm assembly, crank arm,and front sprocket for a bicycle.

BACKGROUND

Typically, in the field of bicycles, the expression “right crank armassembly” is used to indicate an assembly comprising a right crank armand at least one front sprocket coupled with the right crank arm. Thefront sprocket, in particular, is the toothed wheel adapted to drive thechain of the bicycle for the motion transmission to the rear wheel ofthe bicycle, such motion being imparted by the cyclist through pedaling.

In conventional bicycles, the right crank arm is directly coupled withthe front sprocket at respective surfaces defined on respective frontfaces of such components. In particular, defining as inner side of thecrank arm and of the front sprocket the one intended to face, in use,towards the frame of the bicycle and as outer side the one opposite theinner side and intended to face, in use, towards the outside, thecoupling between right crank arm and front sprocket typically takesplace at one of the sides of the crank arm and at one of the sides ofthe front sprocket.

It has been observed that, in operation, the front sprocket elasticallydeforms due to the stresses to which it is subjected during pedaling.Such a deformation leads to a decrease in the transmission efficiency ofthe motion imparted through the crank arm assembly.

In particular, the crank arm transmits to the front sprocket the forcethat the cyclist exerts upon the pedals of the bicycle. Such a forceacts in a plane parallel to the middle plane of the front sprocket andits direction of application and intensity change at each angularposition of the pedal. This stress therefore causes a variable lateralflexing deformation of the front sprocket. Considering also that thechain exerts on a portion of the front sprocket a force opposing theforward movement of the front sprocket, the resulting stress on thefront sprocket is a twisting stress. Therefore, the consequentdeformation of the front sprocket is a twisting deformation.

Such a deformation occurs in all conventional front sprockets, even ifthey are made from metallic material, but it is rather accentuated inthe case of front sprockets made from lightweight materials.

Indeed, it is known, above all in the field of racing bicycles, to usefront sprockets made from light alloys, like for example aluminumalloys, and composite alloys, i.e. made partly from metallic materialand partly from another material, like for example carbon fiber.

The right crank arm assemblies of the prior art typically comprise astar-shaped right crank arm. Such a crank arms comprise, in particular,a plurality of coupling arms having at respective free ends, a portionfor fixing to the front sprocket.

The Applicant has found that, in order to reduce the overall weight ofknown assemblies to the minimum, the coupling arms of the crank arms andthe corresponding coupling elements of the front sprockets are made withvery low thickness, this causing the twisting of the front sprockets.

The Applicant has also found that, also in the case of strengthenedcrank arms, front sprockets made from light material still continue tobend a lot.

SUMMARY

The technical problem that the crank arm assembly seeks to overcome isto reduce as much as possible the twisting deformations of frontsprockets associated with right crank arms, in particular of frontsprockets made from light material, so as not to penalize thetransmission efficiency of the motion imparted through the crank armassembly.

The crank arm therefore relates, in a first aspect thereof, to a rightcrank arm assembly for a bicycle, comprising a right crank arm and atleast one front sprocket coupled with said crank arm at least one firstcoupling portion of the crank arm, wherein said at least one frontsprocket has an inner side intended, in use, to face towards the frameof the bicycle and an outer side opposite the inner side, said assemblyfurther comprising at least one first crank arm element which acts incontact with said at least one front sprocket on one of said sides,wherein it comprises at least one second crank arm element which acts incontact with said at least one front sprocket on the other of saidsides.

BRIEF DESCRIPTION OF THE DRAWING(S)

Further characteristics and advantages described herein shall becomeclearer from the following detailed description of some preferredembodiments thereof, made with reference to the attached drawings. Insuch drawings:

FIG. 1 is a front view from the inner side of a right crank arm assemblyaccording to the present invention, comprising a combination of standardfront sprockets;

FIG. 2 is a front view of the outer side of the assembly of FIG. 1;

FIG. 3 is a front view of the inner side of a right crank arm assemblyaccording to the present invention, comprising a combination ofcompact-type front sprockets;

FIG. 4 is a front view of the outer side of the assembly of FIG. 3;

FIG. 5 is a section view according to the section line V-V of FIG. 3;

FIGS. 6 to 8 are respectively a perspective view, a view of the innerside and a view of the outer side of a right crank arm according to thepresent invention, such a crank arm being used in the assembly of FIG.1;

FIG. 9 is an enlarged section view according to the line IX-IX of FIG.7;

FIGS. 10 and 11 are respectively perspective views of the inner side andof the outer side of a front sprocket according to the presentinvention, such a front sprocket being used in the assembly of FIG. 1;

FIG. 12 shows a mounting step of the front sprocket of FIGS. 10 and 11onto the crank arm of FIGS. 6 to 8;

FIG. 13 is a front view of the outer side of an alternative embodimentof the crank arm described herein;

FIG. 14 is a perspective view of the inner side of an alternativeembodiment of the front sprocket described herein;

FIGS. 15 and 16 are respectively a front view of the outer side and aperspective view sectioned according to the line XVI-XVI of FIG. 15, ofan alternative embodiment of a right crank arm assembly according to thepresent invention;

FIG. 17 is a front view of the outer side of a further embodiment of aright crank arm assembly according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Introduction

Advantageously, the provision in the crank arm of elements adapted toact in contact with the two opposite sides of the front sprocketeffectively blocks the twisting deformation of the front sprocket duringpedaling, to the great advantage of the transmission efficiency of themotion imparted through the right crank arm assembly described herein.

Preferably, the crank arm comprises a main body and said at least onefirst crank arm element and at least one second crank arm element areintegral with the main body. However, an alternative embodiment of theassembly described herein is foreseen in which said at least one firstcrank arm element and at least one second crank arm element are distinctfrom, and associated with the main body of the crank arm.

Preferably, the coupling between front sprocket and crank arm at theaforementioned coupling portion is a dismountable coupling, so as to beable, if required or necessary, to replace the front sprocket or thecrank arm for maintenance or repairs.

In the preferred embodiments of the assembly described herein, the crankarm comprises a plurality of first crank arm elements and a plurality ofsecond crank arm elements. In particular, the crank arm elements arepreferably at least two per side, possibly four, but embodiments with adifferent number, even an odd number, of crank arm elements are notexcluded. Advantageously, the provision of many crank arm elements perside allows a contact between crank arm and front sprocket to beobtained that is particularly stable and effective in blocking thetwisting deformation of the front sprocket.

Preferably, at least some of said at least one first crank arm elementand at least one second crank arm element extend at least partiallyalong respective non-radial directions with respect to a rotational axisof the crank arm. Advantageously, unlike assemblies of the prior artwhere contact occurs only at the ends of the arms of the crank armextending radially with respect to the rotational axis of the crank arm,in the assembly described herein the contact between front sprocket andcrank arm occurs at surfaces having a greater extension compared to theprior art. The desired stability and effectiveness of the contactbetween crank arm and front sprocket is thus ensured.

Preferably, at least some of said at least one first crank arm elementand at least one second crank arm element extend at least partiallycircumferentially around said rotational axis of said crank arm, morepreferably along respective arcs of circumference having an angularextension of less than 360°. Advantageously, in the crank arm of theassembly described herein, areas can in this way be identified in whichthe crank arm elements are not present. Such areas are used to allow andfacilitate the insertion of the front sprocket between, and its removalfrom, the axial space defined on the crank arm between the first and thesecond crank arm elements. In this way it is possible to obtain thecontact of the front sprocket with the crank arm at both sides of thefront sprocket at the same time ensuring the removability of thecoupling between front sprocket and crank arm to allow possible repairor replacement of the front sprocket or crank arm.

Preferably, such an angular extension is less than 360° and greater thanor equal to 15°, more preferably it is between 15° and 100°, even morepreferably between 30° and 75°.

Preferably, said at least one first crank arm element and at least onesecond crank arm element act in abutment onto said at least one frontsprocket at different angular positions of the crank arm. The Applicanthas indeed observed that, during pedaling, the front sprocket twists ondifferent sides from one point to another. The Applicant has thereforethought to position, at each point of the front sprocket, crank armelements only at the side in which the front sprocket twists. The crankarm elements are thus only positioned where they actually perform theircounteraction to the twisting deformation of the front sprocket. In thisway a substantial saving in weight of the crank arm is obtained inaddition to an excellent result in terms of prevention of twistingdeformation of the front sprocket.

Preferably, said at least one first crank arm element and at least onesecond crank arm element extend from opposite sides with respect to saidat least one first coupling portion. The Applicant has indeed foundthat, with reference to a coupling portion with the crank arm, the frontsprocket twists on opposite sides before and after such a couplingportion, and has thus thought to position the first crank arm elementson the opposite side to the second crank arm elements with respect toeach coupling portion.

Even more preferably, said at least one second crank arm element isarranged in a position that precedes said at least one first couplingportion with reference to the direction of rotation of said crank armduring pedaling and said at least one first crank arm element isarranged in a position that follows said at least one first couplingportion with reference to said direction of rotation. The Applicant hasindeed found that such a geometry provides effective opposition to thedeformation of the front sprocket.

Preferably, the crank arm comprises at least one abutment surfaceadapted to allow the correct angular positioning of the crank arm withrespect to said at least one front sprocket. More preferably, said atleast one abutment surface is defined at least partially in said atleast one second crank arm element. Advantageously, it is in this waypossible to obtain the correct angular positioning of the crank arm withrespect to the front sprocket without needing to provide specialabutment elements. Moreover, the abutment surfaces advantageouslyconstitute additional means for making the front sprocket rotate.Indeed, thanks to the provision of the aforementioned abutment surfacesthe right crank arm assembly described herein would be able to transmittorque in the direction of pedaling even if the front sprocket is notfixed to the right crank arm through proper screws.

Even more advantageously, the provision of the abutment surfaces ensuresthat when the front sprocket is in abutment onto the crank arm, thefirst and second crank arm elements cooperate to hold the front sprocketin the axial space defined between them, thus leaving both of theoperator's hands free, who can thus easily screw in the screws to firmlycouple the front sprocket with the crank arm.

In a particularly preferred embodiment thereof, the assembly describedherein comprises a first front sprocket having a first diameter and atleast one second front sprocket having a second diameter different tothe first diameter, wherein the first front sprocket is coupled with thecrank arm at said at least one first coupling portion and said at leastone second front sprocket is coupled with the crank arm at least onesecond coupling portion different from said at least one first couplingportion.

Advantageously, the provision on the crank arm of different couplingportions for the different front sprockets makes the removal of thefront sprockets for possible repairs or replacement quicker and easier.This cannot be obtained in assemblies of the prior art, wherein all ofthe front sprockets are coupled with the crank arms at the same couplingportions of the crank arm.

Even more preferably, said at least one first coupling portion isdefined at a first circumference having its centre at the rotationalaxis of the crank arm and said at least one second coupling portion isdefined at least one second circumference concentric to the firstcircumference and having a different diameter to that of the firstcircumference.

Advantageously, the provision of front sprockets of different diametercoupled at different coupling portions of the crank arm allows a largenumber of combinations of front sprockets of different size to be made,such combinations also comprising very small front sprockets and verybig front sprockets. In this respect, it should be noted that, inconventional assemblies, the only combinations used are those known as“standard”, comprising small front sprockets with a number of teeth ofbetween 38 and 44 and large front sprockets with a number of teeth ofbetween 52 and 56, and “compact”, comprising small front sprockets witha number of teeth of between 32 and 36 and large front sprockets with anumber of teeth of between 46 and 50. The assembly described herein, onthe other hand, allows different combinations to “standard” or “compact”to be adopted, like for example mixed combinations.

The Applicant has also found that, in conventional crank arms, the armsare sized to give the maximum resistance to twisting in combination withfront sprockets of predetermined size. The result of this is that, inthe case in which the cyclist intends to use front sprockets ofdifferent sizes and wants to maintain an acceptable structural rigidity,he is forced to replace also the right crank arm. This, as well asconstituting a trouble for the cyclist, implies that the crank armmanufacturer needs to design, manufacture and commercialize crank armsof different sizes.

Advantageously, with an assembly like the one described herein in whichfront sprockets of different diameter are coupled at different couplingportions of the crank arm, it is no longer necessary to producedifferent sized crank arms for each combination of front sprocketsintended to be used, nor does the cyclist have to change the crank armeach time he changes the combination of front sprockets in order to beable to maintain the desired structural rigidity. The present inventionis therefore advantageous both for the cyclist and for the crank armmanufacturer.

Preferably, said at least one first coupling portion is defined along atleast one first substantially radial direction with respect to saidrotational axis of the crank arm and said at least one second couplingportion is defined along at least one second substantially radialdirection different from said first substantially radial direction.

Even more preferably, the assembly described herein comprises at leasttwo first coupling portions arranged at a first predetermined angulardistance one from the other and at least two second coupling portionsarranged at a second predetermined angular distance one from the other,the second predetermined angular distance being shorter than the firstpredetermined angular distance.

In the preferred embodiment of the assembly described herein, the mainbody of the crank arm comprises a first body portion that couples with abicycle pedal and a second body portion that couples with said at leastone front sprocket and with a shaft of a bottom bracket assembly of abicycle, wherein said second body portion comprises at least one armthat couples with said at least one front sprocket extendingsubstantially radially with respect to a rotational axis of the crankarm, wherein said at least one first coupling portion is defined in saidat least one coupling arm and wherein said at least one first crank armelement and at least one second crank arm element extend from said atleast one coupling arm along non-radial directions on opposite sideswith respect to said at least one first coupling portion.

Preferably, the crank arm comprises a plurality of coupling arms andsaid at least one first crank arm element and at least one second crankarm element extend from at least some of said coupling arms.

In particular, in a first particularly preferred embodiment of theassembly described herein, said at least one second crank arm elementextends cantilevered from a respective coupling arm and, preferably,said at least one first crank arm element extends circumferentiallywithout structural interruption between two adjacent coupling arms. Morepreferably, said at least one second crank arm element extendscantilevered from the coupling arm of said two adjacent coupling armsthat precedes the other coupling arm with reference to the direction ofrotation of the crank arm during pedaling.

However, an embodiment is foreseen in which said at least one firstcrank arm element extends cantilevered from a respective coupling arm.

Preferably, in the case in which the assembly described herein comprisesmore than one front sprocket, said at least one second coupling portionis also defined in said at least one coupling arm. It is not thereforenecessary to provide coupling elements in the crank arm other than thosealready provided for the coupling with the first front sprocket, to thegreat advantage of the weight of the crank arm.

Preferably, the crank arm further comprises an additional couplingportion defined in said first body portion, said first front sprocketand at least one second front sprocket both being coupled with saidcrank arm at said additional coupling portion. In this way a stablecoupling of the front sprockets with the crank arm is achieved withoutweakening the body of the crank arm by providing many coupling pointstherein.

Preferably, the crank arm is made from light metal material or, morepreferably, from composite material. In the latter case, the crank armelements are also made from composite material, so as to obtain acomponent which is particularly light in weight.

Preferably, the assembly described herein comprises at least one firstfront sprocket element that cooperates with said at least one firstcrank arm element and at least one second front sprocket element thatcooperates with said at least one second crank arm element.

More preferably, said at least one first front sprocket element has anangular extension substantially equal to that of said at least one firstcrank arm element. Advantageously, the front sprocket is thus providedwith extended contact elements that give the front sprocket itself acertain rigidity and that thus allow the front sprocket to be madelighter in weight.

Preferably, said at least one front sprocket comprises an annularelement having a radially inner surface from which at least one couplingelement with the crank arm extends cantilevered.

In a preferred embodiment of the assembly described herein, said atleast one first front sprocket element and at least one second frontsprocket element are defined in a body portion of said annular elementextending radially cantilevered from said radially inner surface andcomprising said at least one coupling element.

In an alternative embodiment of the assembly described herein, said atleast one second front sprocket element is defined by a respective bodyportion of said annular element extending radially cantilevered fromsaid radially inner surface, said respective body portion not comprisingsaid at least one coupling element.

Preferably, said annular element comprises a toothed portion thatextends radially towards the outside along a primitive circumferencehaving a predetermined diameter T, and said at least one first frontsprocket element and at least one second front sprocket element areentirely contained in a first area extending radially towards theoutside starting from an ideal circumference having a diameter T′≧aT,where a has a value selected from ⅔, ¾, ⅘, ⅚ or 6/7. Advantageously, thefront sprocket in this case is reduced to a simple toothed band providedwith contact and coupling elements with the crank arm having a veryshort radial extension.

Preferably, the annular element of the front sprocket is made from lightmetal material or composite material. In this way a component which isparticularly light in weight is obtained.

In a second aspect thereof, the present invention relates to a rightcrank arm for a bicycle, comprising a main body adapted to be coupledwith at least one front sprocket of a crankset for a bicycle at leastone first coupling portion of the main body, said at least one frontsprocket having an inner side intended, in use, to face towards theframe of the bicycle and an outer side opposite the inner side, the mainbody comprising at least one first contact element adapted to act onsaid at least one front sprocket on one of said sides, the crank armbeing wherein the main body comprises at least one second contactelement adapted to act on said at least one front sprocket on the otherof said sides.

Throughout the present description and in the subsequent claims, thecontact elements described with reference to the crank arm correspond tothe elements indicated previously as crank arm elements.

Advantageously, the right crank arm described above can be used in theright crank arm assembly discussed above with reference to the firstaspect described herein, thus allowing the advantages mentioned abovewith reference to such a crank arm assembly to be achieved.

Preferably, the right crank arm described above comprises individuallyand/or in combination all of the structural and functional features (bethey essential, preferred and/or advantageous features) described abovewith reference to the crank arm of the right crank arm assemblydescribed herein.

In particular, preferably, said at least one first contact element andat least one second contact element are integral with the main body.However, an embodiment is foreseen in which said at least one firstcontact element and at least one second contact element are distinctfrom, and associated with, said main body.

Preferably, the main body of the crank arm comprises a plurality offirst contact elements and a plurality of second contact elements.

Preferably, at least some of said at least one first contact element andat least one second contact element extend at least partially alongrespective non-radial directions with respect to a rotational axis ofsaid crank arm.

Preferably, at least some of said at least one first contact element andat least one second contact element extend at least partiallycircumferentially around said rotational axis of said crank arm, morepreferably along respective arcs of circumference having an angularextension of less than 360°.

Preferably, such an angular extension is less than 360° and greater thanor equal to 15°, more preferably it is between 15° and 100°, even morepreferably between 30° and 75°.

Preferably, said respective arcs of circumference have different angularpositions with respect to said rotational axis.

Preferably, said at least one first contact element and at least onesecond contact element extend from opposite sides with respect to saidat least one first coupling portion.

More preferably, said at least one second contact element is arranged ina position that precedes said at least one first coupling portion withreference to the direction of rotation of the crank arm during pedalingand said at least one first contact element is arranged in a positionthat follows said at least one first coupling portion with reference tosaid direction of rotation.

Preferably, the main body of the crank arm comprises at least oneabutment surface adapted to allow the correct angular positioning ofsaid crank arm with respect to said at least one front sprocket.

More preferably, said at least one abutment surface is defined at leastpartially in said at least one second contact element.

Preferably, the main body of the crank arm comprises at least one firstcoupling portion with a first front sprocket of a crankset for a bicycleand at least one second coupling portion with at least one second frontsprocket of a crankset for a bicycle having a different diameter fromthe diameter of said at least one first front sprocket, wherein said atleast one second coupling portion is different from said at least onefirst coupling portion.

Preferably, said at least one first coupling portion is defined at afirst circumference having its centre at the rotational axis of saidcrank arm and said at least one second coupling portion is defined atleast one second circumference concentric with said first circumferenceand having a diameter different to that of said first circumference.

Preferably, said at least one first coupling portion is defined along atleast one first substantially radial direction with respect to saidrotational axis and said at least one second coupling portion is definedalong at least one second substantially radial direction different fromsaid first substantially radial direction.

Preferably, the main body of the crank arm comprises at least two firstcoupling portions arranged at a first predetermined angular distance onefrom the other and at least two second coupling portions arranged at asecond predetermined angular distance one from the other, said secondpredetermined angular distance being shorter than said firstpredetermined angular distance.

Preferably, the main body of the crank arm comprises a first bodyportion that couples with a bicycle pedal and a second body portion thatcouples with said at least one front sprocket and with a shaft of abottom bracket assembly of a bicycle, wherein said second body portioncomprises at least one coupling arm with said at least one frontsprocket extending substantially radially with respect to a rotationalaxis of said crank arm, wherein said at least one first coupling portionis defined in said at least one coupling arm and said at least one firstcontact element and at least one second contact element extend from saidat least one coupling arm along non-radial directions on opposite sideswith respect to said at least one coupling portion.

Preferably, said main body comprises a plurality of coupling arms andsaid at least one first contact element and at least one second contactelement extend from at least some of said coupling arms.

In particular, in a first particularly preferred embodiment of the crankarm described herein, said at least one second contact element extendscantilevered from a respective coupling arm and, preferably, said atleast one first contact element extends circumferentially without anystructural interruption between two adjacent coupling arms. Morepreferably, said at least one second contact element extendscantilevered from the coupling arm of said two adjacent coupling armsthat precedes the other coupling arm with reference to the direction ofrotation of the crank arm during pedaling.

However, an embodiment is foreseen in which said at least one firstcontact element extends cantilevered from a respective coupling arm.

Preferably, in the case in which the crank arm described herein isadapted to be coupled with at least two front sprockets, said at leastone second coupling portion is also defined in said at least onecoupling arm.

Preferably, the main body of the crank arm is made from light metalmaterial or from composite material.

In a third aspect thereof, the present invention relates to a frontsprocket for a crankset of a bicycle, comprising an annular elementhaving at least one coupling portion with a right crank arm of abicycle, said crank arm having an inner side intended, in use, to facetowards the frame of the bicycle and an outer side opposite said innerside, said annular element comprising at least one first contact elementadapted to act in abutment on said crank arm on one of said sides,wherein said annular element comprises at least one second contactelement adapted to act in abutment on said crank arm on the other ofsaid sides.

Throughout the present description and in the subsequent claims, thecontact elements described with reference to the front sprocketcorrespond to the element indicated previously as front sprocketelements.

Advantageously, the front sprocket described above can be used in theright crank arm assembly discussed above with reference to the firstaspect described herein and therefore allows the advantages mentionedabove with reference to such a crank arm assembly to be obtained.

Preferably, the front sprocket described herein comprises individuallyand/or in combination all of the structural and functional features (bethey essential, preferred and/or advantageous features) described withreference to the front sprocket of the right crank arm assembly of thefirst aspect described herein.

In particular, said annular element preferably comprises a plurality offirst contact elements and a plurality of second contact elements.

Preferably, said at least one first contact element and at least onesecond contact element extend at least partially along respectivenon-radial directions with respect to a rotational axis of said frontsprocket.

More preferably, said at least one first contact element and at leastone second contact element extend at least partially circumferentiallyaround said rotational axis of said front sprocket along respective arcsof circumference having an angular extension of less than 360°.

Preferably, said angular extension is less than 360° and greater than orequal to 15°, more preferably it is between 15° and 100°, even morepreferably between 30° and 75°.

Even more preferably, said respective arcs of circumference havedifferent angular positions with respect to said rotational axis.

Preferably, said at least one first contact element and at least onesecond contact element extend from opposite sides with respect to saidat least one coupling portion.

More preferably, said at least one second contact element is arranged ina position that precedes said at least one coupling portion withreference to the direction of rotation of the front sprocket duringpedaling and said at least one first contact element is arranged in aposition that follows said at least one coupling portion with referenceto said direction of rotation.

Preferably, said annular element comprises at least one abutment surfaceadapted to allow the correct angular positioning of said front sprocketwith respect to said crank arm.

More preferably, said at least one abutment surface is defined at leastpartially in said at least one second contact element.

Preferably, said annular element comprises a radially inner surface fromwhich at least one element for coupling with said crank arm extendsradially, said at least one coupling portion being defined in said atleast one coupling element.

In a first embodiment of the front sprocket described herein, said atleast one first contact element and at least one second contact elementare defined in a body portion of said annular element extending radiallycantilevered from said radially inner surface and comprising said atleast one coupling element.

In an alternative embodiment of the front sprocket described herein,said at least one second contact element is defined by a respective bodyportion of said annular element extending radially cantilevered fromsaid radially inner surface, said respective body portion not comprisingsaid at least one coupling element.

Preferably, said at least one first contact element extendscircumferentially without structural interruption between two adjacentcoupling elements.

Preferably, said annular element comprises a toothed portion thatextends radially towards the outside along a primitive circumferencehaving a predetermined diameter T, wherein said at least one firstcontact element and at least one second contact element are entirelycontained in a first area extending radially towards the outsidestarting from an ideal circumference having a diameter T′≧aT, where ahas a value selected from ⅔, ¾, ⅘, ⅚ or 6/7.

Preferably, said annular element is made from a light metal alloy orcomposite alloy.

In a fourth aspect thereof, the present invention relates to a rightcrank arm assembly for a bicycle, comprising a right crank arm and atleast one front sprocket coupled with said crank arm, wherein itcomprises at least one crank arm element which acts in contact with saidat least one front sprocket and that extends along a non-radialdirection with respect to a rotational axis of said crank arm.

Advantageously, the provision in the crank arm of contact elementsextending along a non-radial direction allows a contact of the crank armon the front sprocket to be obtained that is more stable and effectivethan what occurs in the assemblies of the prior art, where the contactoccurs only at the ends of the arms of the crank arm extending radiallywith respect to the rotational axis of the crank arm. In this way it ispossible to limit the deformation of the front sprocket, with aconsequent advantage in terms of motion transmission.

Preferably, the assembly discussed above with reference to the fourthaspect described herein comprises individually and/or in combination allof the features described above with reference to the assembly of thefirst aspect described herein, thus achieving all of the advantagesdiscussed above with reference to such an assembly.

In particular, preferably, the crank arm of the assembly of the fourthaspect described herein comprises at least one coupling arm with said atleast one front sprocket extending along a substantially radialdirection, wherein said at least one crank arm element extends from saidat least one coupling arm.

More preferably, the crank arm comprises a plurality of coupling arms,wherein said at least one crank arm element extends from at least someof said coupling arms.

Preferably, said at least one crank arm element extends at leastpartially circumferentially around said rotational axis of said crankarm along an arc of circumference having a predetermined angularextension.

In a specific embodiment of the assembly described herein, such anangular extension is equal to 360°.

In an alternative embodiment, such an angular extension is less than360° and greater than or equal to 15, and is preferably between 15° and100°, more preferably between 30° and 75°.

As already stated with reference to the crank arm assembly discussedabove with reference to the first aspect described herein, said at leastone crank arm element extends circumferentially without structuralinterruption between two adjacent coupling arms. However, a variant isforeseen in which said at least one crank arm element extendscantilevered from said at least one coupling arm.

Preferably, said at least one front sprocket has an inner side intended,in use, to face towards the frame of the bicycle and an outer sideopposite said inner side and said at least one crank arm element isactive on said at least one front sprocket on said outer side.

Preferably, said crank arm is made from light metal material or fromcomposite material.

Preferably, the assembly described herein comprises at least one frontsprocket element that cooperates with said at least one crank armelement, wherein said at least one front sprocket element has an angularextension substantially equal to that of said at least one crank armelement.

Preferably, said at least one front sprocket comprises an annularelement having a radially inner surface from which at least one couplingelement with said crank arm extends radially cantilevered.

Preferably, said at least one coupling element is structurally distinctfrom said at least one front sprocket element.

Preferably, said annular element comprises a toothed portion thatextends radially towards the outside along a primitive circumferencehaving a predetermined diameter T, wherein said at least one frontsprocket element and said at least one coupling element are entirelycontained in a first area extending radially towards the outsidestarting from an ideal circumference having a diameter T′≧aT, where ahas a value selected from ⅔, ¾, ⅘, ⅚ or 6/7.

Preferably, said annular element is made from light metal material orfrom composite material.

In a fifth aspect thereof, the present invention relates to a rightcrank arm for a bicycle, comprising a main body adapted to be coupledwith at least one front sprocket of a crankset of a bicycle, whereinsaid main body comprises at least one contact element with said at leastone front sprocket that extends along a non-radial direction withrespect to a rotational axis of said crank arm.

Throughout the present description and in the subsequent claims, thecontact elements described with reference to the crank arm correspond tothe elements indicated previously as crank arm elements.

Advantageously, the crank arm described above can be used in the rightcrank arm assembly discussed above with reference to the fourth aspectdescribed herein, and thus allows the advantages mentioned above withreference to such a crank arm assembly to be achieved.

Preferably, the crank arm described herein comprises individually and/orin combination all of the structural and functional features (be theyessential, preferred and/or advantageous features) described withreference to the crank arm of the right crank arm assembly of the fourthaspect described herein.

In a sixth aspect thereof, the present invention relates to a frontsprocket for a crankset of a bicycle, comprising an annular elementadapted to be coupled with a right crank arm of a bicycle, wherein saidannular element comprises at least one contact element with said crankarm extending along a non-radial direction with respect to a rotationalaxis of said front sprocket.

Throughout the present description and in the subsequent claims, thecontact elements described with reference to the front sprocketcorrespond to the elements indicated previously as front sprocketelements.

Advantageously, the front sprocket described above can be used in theright crank arm assembly discussed above with reference to the fourthaspect described herein, and therefore allows the advantages mentionedabove with reference to such a crank arm assembly to be achieved.

Preferably, the front sprocket described herein comprises individuallyand/or in combination all of the structural and functional features (bethey essential, preferred and/or advantageous features) described withreference to the front sprocket of the right crank arm assembly of thefourth aspect described herein.

In a seventh aspect thereof, the present invention relates to a rightcrank arm assembly for a bicycle, comprising a right crank arm and atleast one front sprocket coupled with said crank arm at least onecoupling portion of said at least one front sprocket, wherein itcomprises at least one front sprocket portion which acts in contact withsaid crank arm and which is structurally distinct from said at least onecoupling portion.

Advantageously, the provision in the front sprocket of contact portionswhich are structurally distinct from the coupling portions allows acontact of the crank arm to be made on the front sprocket that is morestable and effective that what occurs in the assemblies of the priorart, where the contact only occurs at the ends of the arms of the crankarm extending radially with respect to the rotational axis of the crankarm. In this way it is possible to limit the deformation of the frontsprocket, with a consequent advantage in terms of transmission ofmotion.

Preferably, the assembly discussed above with reference to the seventhaspect described herein comprises individually and/or in combination allof the structural and functional features discussed above with referenceto the assembly of the first aspect described herein, thus obtaining allof the advantages discussed above with reference to this assembly.

In particular, preferably, said at least one front sprocket portion isdefined in at least one front sprocket element that extends radiallycantilevered from a radially inner surface of said at least one frontsprocket and said at least one coupling portion is defined in at leastone first coupling element that extends radially cantilevered from saidradially inner surface in a different angular position to that of saidat least one front sprocket element.

Preferably, said front sprocket comprises an annular element made from alight metal material or from a composite material.

Preferably, said annular element comprises a toothed portion thatextends radially towards the outside along a primitive circumferencehaving a predetermined diameter T, wherein said at least one frontsprocket element and said at least one first coupling element areentirely contained in a first area extending radially towards theoutside starting from an ideal circumference having a diameter T′≧aT,where a has a value selected from ⅔, ¾, ⅘, ⅚ or 6/7.

Preferably, the assembly described herein comprises at least one crankarm element adapted to cooperate with said at least one front sprocketelement and at least one second coupling element adapted to cooperatewith said at least one first coupling element.

Preferably, said crank arm is made from a light metal material or from acomposite material.

In an eighth aspect thereof, the present invention relates to a frontsprocket for a crankset of a bicycle, comprising an annular elementadapted to be coupled with a right crank arm of a bicycle at a couplingportion of said annular element, wherein said annular element comprisesat least one contact portion with said crank arm which is structurallydistinct from said at least one coupling portion.

Throughout the present description and in the subsequent claims, thecontact elements described with reference to the front sprocketcorrespond to the elements indicated previously as front sprocketelements.

Advantageously, the front sprocket described above can be used in theright crank arm assembly discussed above with reference to the seventhaspect described herein, and thus allows the advantages mentioned abovewith reference to such a crank arm assembly to be obtained.

Preferably, the front sprocket described herein comprises individuallyand/or in combination all of the structural and functional features (bethey essential, preferred and/or advantageous features) described withreference to the front sprocket of the right crank arm assembly of theseventh aspect described herein.

DESCRIPTION

With reference to FIGS. 1 and 2, a first embodiment of a right crank armassembly according to the present invention is indicated with 1. Theassembly 1 comprises a right crank arm 5, a front sprocket of largerdiameter 10 (hereafter indicated as big front sprocket) and a frontsprocket of smaller diameter 15 (hereafter indicated as small frontsprocket). Alternative and not illustrated embodiments are foreseen inwhich the assembly 1 comprises just one front sprocket, for example foruse on a racing track, or more than two front sprockets, for examplethree.

Throughout the present description and in the subsequent claims, the“inner side” of the assembly 1, of the crank arm 6 and/or of the frontsprockets 10 and 15 shall indicate the side visible in FIGS. 1 and 3,i.e. the one facing towards the frame of the bicycle when the assembly 1is mounted in the bottom bracket assembly. On the other hand “outerside” shall indicate the side opposite the inner side, visible in FIGS.2 and 4.

Throughout the present description and in the subsequent claims,moreover, “previous position” or “following position” shall respectivelyindicate the position of an element that precedes and that follows areference element in the direction of rotation of the crank arm, wherethe rotation is in the direction such as to transmit driving force tothe rear wheel.

The right crank arm 5 described herein can be made from metallicmaterial, like a light alloy, or from composite material, comprisingstructural fibers incorporated in a polymeric material. Typically, thestructural fibers are selected from the group consisting of carbonfibers, glass fibers, aramid fibers, ceramic fibers, boron fibers andcombinations thereof, carbon fibers being preferred. Preferably, thepolymeric material of the body of the component is thermosetting.However, the possibility of using a thermoplastic material is notexcluded. More preferably, the polymeric material comprises an epoxyresin. While these materials are preferred, they are not limiting toother materials that may be chosen.

The arrangement of said structural fibers in the polymeric material canbe a random arrangement of pieces or sheets of structural fibers, asubstantially unidirectional ordered arrangement of fibers, asubstantially bidirectional ordered arrangement of fibers, or acombination of the above.

In an alternative embodiment, the fibers are organized in a fabric woundwith continuity around a recess, as described in patent EP 1270394 andin European patent applications n^(o) 06425086 and 06425087 (U.S.application Ser. Nos. 11/675,279 and 11/501,656) to the same Applicantthe content of which are incorporated herein by reference as if fullyset forth.

With particular reference to FIGS. 6 to 8, the right crank arm 5comprises a main body 20 having a first end 21 for coupling with a pedal(not illustrated) and a second end 22 for coupling with the frontsprockets 10 and 15 and with a shaft of a bottom bracket assembly (notillustrated). In particular, the second end 22 comprises a hole 23 forhousing the shaft of the bottom bracket assembly. In alternative and notillustrated embodiments but known to a person of ordinary skill in theart, the shaft is removably coupled with the right crank arm, or it isan integral part thereof.

A support structure 25 of the front sprockets 10 and 15 is providedabout the hole 23, comprising four coupling arms (or spokes) 27 thatextend substantially radially around the hole 23 inside of which arotational axis X of the crank arm 5 is defined.

At the respective free end portions 28 the arms 27 are connected in setsof two by a reinforcing element 30, preferably extendingcircumferentially around the rotational axis X of the crank arm 5 andmade in the form of an arc of circle.

Each reinforcing element 30 that connects a pair of arms 27 comprises acontact surface 32 at the outer side of the big front sprocket 10.

The contact surfaces 32 preferably have an angular extension α (FIG. 7)greater than or equal to 15°, preferably between 15° and 100°, morepreferably between 30° and 75° and are arranged at an angular distance βfrom the middle plane Π of the elongated body 20, where β is preferablybetween 30° and 90°.

In an alternative embodiment of the crank arm 5 (not illustrated) thepairs of arms 27 connected by the element 30 are replaced by a singlearm of equal angular extension.

Now considering the pairs of arms 27 connected together by the element30, the arm 27 of each of them coming first in the direction of rotationω of the right crank arm 5 around the rotational axis X of the crank arm5, comprises an element 35 extending cantilevered in the circumferentialdirection in the direction of rotation ω. Each element 35 comprises acontact surface 40 at the inner side of the big front sprocket 10.

Coupling portions 44 with the big front sprocket 10 are defined at thefree ends 28 of each arm 27. The element 30 connects the coupling arms27 right at such coupling portions 44. The coupling portions 44 areprovided with coupling holes 45.

The coupling portions 44 with the ends 28 of the arms 27 connected bythe element 30 are arranged at an angular distance γ from each other ofbetween 45° and 95°, and the coupling portion 44 closest to theelongated body 20 is arranged at an angular distance μ of between 35°and 85° from the plane Π.

An additional coupling hole 46 with the front sprocket 10 is preferablyprovided on a portion of the elongated body 20 (FIG. 7).

The section of FIG. 9 shows in detail an example embodiment of thecoupling portions 44 in the case in which the right crank arm 5 is madefrom composite material. The coupling portions 44 are in this casepreferably defined by metallic inserts 50 provided with a threaded hole52 for the insertion of a screw (not illustrated). The outer surface 54of the inserts 50 is irregular, and preferably threaded, so as to beable to be better held in the composite material, to which it is fixedby gluing or by direct adhesion due to a co-moulding process.

An alternative embodiment of the assembly described herein is foreseenin which the threaded hole 52 is directly made in the compositematerial.

As shown in detail in FIG. 9, the crank arm 5 described herein furthercomprises, in a preferred embodiment thereof, second coupling portions47 used for the coupling of the small front sprocket 15. The couplingportions 47 are preferably made identical to the coupling portions 44and comprise coupling holes 48.

The coupling portions 44 and 47 are at different distances from therotational axis X of the right crank arm 5. In particular, their axes ofsymmetry S1 and S2 lie on two ideal circumferences of differentdiameter.

As illustrated in FIGS. 1, 3, 6, 7 and 12, the coupling portions 44 and47 are preferably non-radially aligned with each other. Indeed, thecoupling portions 44 are at smaller angular distances γ apart than theangular distances between the coupling portions 47.

Both the big front sprocket 10 and the small front sprocket 15 arecoupled with the main body 20 of the crank arm 5 at the additionalcoupling portion 46.

With particular reference now to the section illustrated in FIG. 5, in apreferred embodiment described herein the contact elements 30 and 35respectively at the outer side and at the inner side of the big frontsprocket 10 are located substantially at the opposite side with respectto the coupling portions 44, identified by the axis of symmetry S1 (saidaxis is parallel to the rotational axis x of the crank arm 5). Inparticular, the surface 32 of the element 30 for contact at the outerside of the front sprocket 10 follows the coupling portion 44 in thedirection of rotation ω, whereas the surface 40 of the element 35 forcontact at the inner side of the front sprocket 10 precedes the couplingportion 44 (FIGS. 6 and 7). The elements 30 and 35 are therefore activein abutment on the front sprocket at different angular positions. Itshould be appreciated from FIG. 5 that the first contact element 30 andthe second contact 40 element are offset from one another along therotational axis of the right crank arm 5; this offset creates a gap inwhich the front sprocket 10 is engaged.

In an alternative embodiment of the crank arm illustrated in FIG. 13 andindicated with 5′, the arms 27′ instead of being connected in sets oftwo through the elements 30, each comprise an element 30′ extendingcantilevered circumferentially around the rotational axis X of the crankarm 5′. Each element 30′ comprises a respective contact surface 32′ atthe outer side of the big front sprocket 10. Each of the arms 27′ alsocomprises a respective contact surface 40′ at the inner side of the bigfront sprocket 10. The contact surfaces 32′ and 40′ are arranged in aposition respectively prior to and after the coupling portion 44 (hiddenin the figures) provided on the arm 27. In this case, the number of arms27 can also be odd, for example three or five.

In a further not illustrated embodiment of the assembly describedherein, just one or in any case just a few of the arms 27 comprise acontact surface 40 at the inner side of the big front sprocket 10,between which the arm 27 immediately following the elongated body 20with reference to the direction of rotation ω of the crank arm 5 andpreferably the arm 27 arranged in a substantially symmetrical positionwith respect to the main body 20 of the crank arm 5.

In accordance with the invention, the contact surfaces 32 and 40 do notlie on the same plane, but a predetermined axial distance D apart (FIG.5). In this way the big front sprocket 10 does not need to be deformedto be inserted between the two contact surfaces. It is thus sufficientfor the front sprocket 10 to have a thickness equal to D in the contactarea with the crank arm 5. Preferably D is equal to or less than themaximum thickness of the big front sprocket 10.

In the embodiments illustrated in the attached figures, the elements 30and 35 are integral with the main body 20 of the crank arm 5, but inother not illustrated embodiments such elements can be made in separatepieces and coupled with the crank arm 5.

In FIGS. 10 and 11, the big front sprocket 10 of the right crank armassembly 1 shown in FIGS. 1 and 2 is illustrated.

Such a front sprocket comprises an annular element 11, preferably madefrom light metal alloy or from composite material, having a radiallyouter annular surface 12 on which a toothed portion 100 (hereafter alsoindicated as toothing) is formed extending radially towards the outsideand a radially inner annular surface 13 from which four elements 98 forcoupling with the crank arm extend radially cantilevered. In particular,the elements 98 are adapted to be coupled with the arms 27 of the crankarm 5 by coupling respective coupling portions defined on the elements98 with the coupling portions 44 defined on the arms 27. The couplingtakes place through screws (not illustrated) inserted in holes 64 formedon each coupling element 98.

On outer side thereof (FIG. 11) the big front sprocket 10 comprises twoelements 55 having respective contact surfaces 60 adapted to contact thecontact surfaces 32 of the elements 30 of the right crank arm 5. Theelements 55 have the same angular extension as the elements 30 and eachelement 55 extends without structural interruption between two adjacentelements 98. What has been stated above with reference to the number,angular position with respect to the coupling portions 44 and angularextension of the elements 30 of the crank arm 5 with respect to therotational axis of the crank arm is therefore also valid for theelements 55 of the front sprocket 10 with reference to the couplingportions defined on the elements 98 and with reference to the rotationalaxis of the front sprocket.

The elements 55 are preferably surmounted in the radial direction by athroat 62 extending according to an arc of circle.

At the ends of the elements 55 the holes 64 for the passage of thescrews that insert into the inserts 50 of the right crank arm 5 areformed.

On the inner side of the front sprocket 10 (illustrated in FIG. 10), onthe other hand, a pair of elements 65 are provided having respectivecontact surfaces 66 adapted to contact the contact surfaces 40 of theelements 35 of the right crank arm 5.

The big front sprocket 10 further comprises an additional arm 68 with ahole 69 for the passage of a screw intended to insert into the holeformed in the additional coupling portion 46 of the crank arm 5, in thecase in which such an additional coupling portion is present.

In the embodiment of the big front sprocket 10 illustrated in detail inFIGS. 10 and 11, each contact element 55 and 65 with the crank arm 5 isdefined at a single body portion 14 of the annular element 11 thatextends radially cantilevered towards the centre of the front sprocket10 from inner surface 13 thereof and that also comprises a pair ofcoupling elements 98. The elements 55, 65, and 98 are therefore all anintegral part of the body portion 14.

FIG. 14 shows an alternative embodiment of the big front sprocket,indicated with 10. In such an embodiment no single body portion 14 thatcomprises the elements 65 and 98 can be identified. Indeed, the bodyportion 14 here comprises just the contact element 55 and a pair ofelements 98 for coupling with the crank arm 5, whereas the contactelements 65 with the crank arm are defined at further and respectivebody portions 140, distinct and separate from the body portion 14 of theannular element 11, which also extend radially cantilevered from theinner surface 14 of the annular element 11 towards the centre of thefront sprocket 10 and which do not comprise the coupling elements 98 andthe contact elements 55 with the crank arm 5.

In such an embodiment, the elements 98 and 65 are made adjacent to thetoothed portion 100 of the front sprocket 10. Preferably, consideringthe diameter T of the primitive circumference of the toothed portion100, the elements 98 and 65 are located and entirely contained in anannular area extending radially between the inner surface of saidannular element and an ideal circumference of diameter T′ such thatT>T′≧aT, where a is selected from ⅔, ¾, ⅘, ⅚ or 6/7.

Preferably, the aforementioned inner surface is defined at an idealcircumference arranged at least 1 mm radially towards the inside fromthe toothed portion 100.

The front sprocket 10 in this case therefore reduces to a toothed bandprovided with radial projections constituting the coupling elements 98and the contact elements 55 and 65 and having a short radial extension.Consequently, the maximum radial extension of the coupling arms providedin the crank arm is defined by a circumference of diameter T″ (see FIGS.2 and 4) such that T>T″>T′, where the difference between T and T″ issimply given by the need to leave a free front sprocket portion which issufficient to allow the engagement of the teeth with a chain.

With particular reference to FIG. 4, if L indicates the length of thearm of the crank arm (such a length being commercially set at 170 mm,172.5 mm and 175 mm), the crank arm of the assembly described herein issized so that the ratio L/T″ is between 0.7 and 1, preferably between0.8 and 0.9.

A not illustrated embodiment is foreseen in which the front sprocket hascoupling elements 98 and contact elements 55 and 65 of short extensionas described above with reference to FIG. 14 and all forming part of asingle body portion 14 as described above with reference to FIG. 11.

It should be noted how, in all of the embodiments of the front sprocket10 of the assembly described herein, the contact portions of the frontsprocket 10 with the crank arm 5 are structurally and physicallydistinct from the respective coupling portions.

In the case of use of the front sprocket of FIG. 11 or of the notillustrated embodiment in which the front sprocket has coupling elements98 and contact elements 55 and 65 of short extension as described abovewith reference to FIG. 14 and all forming part of a single body portion14 as described above with reference to FIG. 11, the crank arm of theassembly described herein has coupling arms having a greater radialextension than those of conventional crank arms. In particular, while inconventional crank arms the diameter of the ideal circumference definedby the coupling holes at the big front sprocket and at the small frontsprocket is 130 mm or 135 mm in the case of standard combinations and110 mm in the case of compact combinations, in the crank arm of theassembly described herein the diameter of the ideal circumferencedefined by the holes 45 for coupling with the big front sprocket 10 iswithin an annular area having an inner diameter greater than or equal to150 mm and an outer diameter less than or equal to 180 mm, preferably aninner diameter greater than or equal to 160 mm and an outer diameterless than or equal to 170 mm, whereas that of the ideal circumferencedefined by the holes 48 for coupling with the small front sprocket 15 iswithin an annular area having an inner diameter greater than or equal to100 mm and an outer diameter less than or equal to 130 mm, preferably aninner diameter greater than or equal to 110 mm and an outer diameterless than or equal to 120 mm.

FIGS. 1 and 2 show a right crank arm assembly comprising a combinationof standard front sprockets, i.e. a small front sprocket with a minimumof 39 teeth coupled with a big front sprocket with a number of teeth ofbetween 52 and 56 (53 in the front sprocket 10 illustrated).

However, the right crank arm 5 illustrated in FIGS. 6, 7 and 8 cansupport a wide range of combinations of front sprockets, for example acompact combination, as illustrated in FIGS. 3 and 4, in which the smallfront sprocket 15′ has a minimum number of teeth equal to 34 and the bigfront sprocket 10′ has a number of teeth of between 46 and 50 (48 in thecombination illustrated).

It should however be noted that the right crank arm 5 allows any size offront sprockets to be mounted, for which reason it is also possible toadopt combinations of front sprockets different to the standard andcompact ones, in particular mixed combinations.

As illustrated in FIGS. 6, 7, 8, 13, the crank arm 5, 5′ furthercomprises abutment surfaces 70, 70′ adapted to allow the correct angularpositioning of the crank arm with respect to the front sprocket 10. Suchsurfaces 70, 70′ are defined at a free end of the contact element 35,35′ with the crank arm 5, 5′. Further abutment surfaces 72 are providedat a body portion of the element 35 that extends on the opposite side,with respect to the coupling arm 27, to the one at which the abutmentsurface 70 is defined. The abutment surfaces 70 and 72 cooperate inabutment with corresponding abutment surfaces 74, 76 defined in the bigfront sprocket 10.

FIG. 12 illustrates the way to mount a big front sprocket 10 on a rightcrank arm 5. In particular, the big front sprocket 10 is brought incontact with the right crank arm 5 so that the contact surfaces 32 ofthe elements 30 of the crank arm 5 come into contact with the contactsurfaces 60 of the elements 55 of the front sprocket 10. At this pointthe right crank arm 5 is rotated with respect to the front sprocket 10in the same direction of rotation ω in which it rotates during pedaling.The crank arm 5 shall move with respect to the front sprocket until theabutment surfaces 70 and 72 of the right crank arm 5 make contact withthe corresponding abutment surfaces 74 and 76 of the front sprocket 10.At this point, the contact surfaces 40 of the elements 35 of the crankarm 5 shall be in abutment with the contact surfaces 66 of the elements65 of the front sprocket 10. As a result of this, when the surfaces 74and 76 of the front sprocket 10 are in abutment with the surfaces 70 and72 of the crank arm, the contact surfaces 32, 40, 60 and 66 cooperatewith each other to keep it in position and the operator has both handsfree to fix the screws.

It should be appreciated that the first contact element 55 and thesecond contact element 65 are offset from one another along a rotationalaxis of the annular element 11.

Now with reference to FIGS. 15 and 16, a further embodiment of the rightcrank arm assembly according to the present invention is illustrated,indicated with 200.

The right crank arm assembly 200 comprises a right crank arm 205,preferably made from composite material, comprising a coupling portion210 with an annular toothed band 215. The coupling portion 210preferably comprises an annular-shaped outer peripheral portion 225coupled with the elongated body 220 of the crank arm 205 through aplurality of coupling arms 230.

The coupling between the coupling portion 210 and the toothed band 215can be of any type capable of transmitting torque. In FIG. 16, as anexample, a shape-coupling is illustrated, in particular toothed,preferably strengthened by gluing, or by the adhesion between compositematerial of the coupling portion 210 and the metal of the toothed band215 obtained by co-molding. Alternatively, the toothed band 215 and thecoupling portion 210 could be made with a threading at their interfaceto be screwed (and then possibly glued) one to the other. According to afurther alternative, the toothed band 215 is fixed onto the couplingportion 210 through screws or other fastening elements.

It should be observed that, although FIG. 16 shows a radial couplinginterface 240 and a circumferential coupling interface 245, it does notexclude embodiments in which the coupling is just circumferential orjust radial (in which case there are no front or rear contact surfacesas for the embodiments of FIGS. 1 to 14). The coupling between thetoothed band 205 and the coupling portion 210 could also be a dovetailcoupling, or a coupling extending along a surface inclined with respectto the rotational axis of the annular toothed band 215.

It should also be observed that, although in FIG. 15 just one annulartoothed band 215 is shown, an embodiment is foreseen in which the rightcrank arm 205 is also coupled with a front sprocket or annular band ofsmaller diameter. The coupling between such an annular band of smallerdiameter and the right crank arm 205 is of the same type as thatdescribed with reference to the annular toothed band 215.

As highlighted in the variant 200′ of FIG. 17, the coupling portion210′, instead of being extended according to a complete ring, cancomprise ring portions 225′, for example having the dimensionsillustrated with reference to the support structure 25 of the crank arm5 of FIGS. 6, 7 and 8. The coupling between the coupling portion 210′and the annular toothed band 215′ is of the same type described for theassembly 200 of FIGS. 15 and 16.

FIG. 17 also shows that the right crank arm assembly 200′ (just like theone 200 of FIG. 15) can comprise a second front sprocket or toothed band216 of smaller diameter with respect to the toothed band 215′. The smallfront sprocket 216 can be of the type illustrated with reference to theright crank arm assemblies of FIGS. 1 to 4, or else a toothed bandsimilar to the toothed band 215′, coupled with the crank arm 205′ in thesame way as the toothed band 215′.

In all of the embodiments described and illustrated, the small frontsprocket 15 is coupled with the right crank arm 5 in a conventional way,i.e. contacting just the outer side. However, an embodiment is foreseenin which the coupling between the small front sprocket 15 and the crankarm 5 is the same as that described for the big front sprocket 10, i.e.contacting both the outer side and the inner side.

Numerous variants of the right crank arm 5 are possible, for example theposition of the contact elements at the outer side and at the inner sideof the big front sprocket can be inverted with respect to the couplingportions, thus performing their contact function in different angularpositions of pedaling. The illustrated example is that in which thecontact elements counteract the twisting of the front sprocket in themost critical condition, i.e. when the pedal has passed the vertical tobegin a new descent, since this is the point at which the cyclist exertsthe maximum thrust. The contact surfaces can also face each other andtherefore are at an identical angular position.

What is claimed is:
 1. Right crank arm assembly for a bicycle,comprising a right crank arm and at least one front sprocket coupledwith said crank arm at least one first coupling portion of said crankarm, wherein said at least one front sprocket has an inner sideintended, in use, to face towards a frame of the bicycle and an outerside opposite said inner side, and wherein said right crank armcomprises at least one first crank arm element which contacts one ofsaid sides of the at least one front sprocket, and at least one secondcrank arm element which is formed in a single piece with the at leastone first crank arm element and contacts the other of said sides of theat least one front sprocket, said at least one first crank arm elementand said at least one second crank arm element being angularly offsetfrom one another along a circumferential direction.
 2. Crank armassembly according to claim 1, wherein said crank arm comprises a mainbody and wherein said at least one first crank arm element and at leastone second crank arm element are formed in a single piece with said mainbody.
 3. Crank arm assembly according to claim 2, wherein said main bodyof said crank arm comprises a first body portion that couples with abicycle pedal and a second body portion that couples with said at leastone front sprocket and with a shaft of a bottom bracket assembly of abicycle, wherein said second body portion comprises at least one armthat couples with said at least one front sprocket extendingsubstantially radially with respect to a rotational axis of said crankarm, wherein said at least one first coupling portion is defined in saidat least one coupling arm and wherein said at least one first crank armelement and at least one second crank arm element extend from said atleast one coupling arm along non-radial directions on opposite sideswith respect to said at least one first coupling portion.
 4. Crank armassembly according to claim 3, wherein said crank arm comprises aplurality of coupling arms and wherein said at least one first crank armelement and at least one second crank arm element extend from at leastsome of said coupling arms.
 5. Crank arm assembly according to claim 3,wherein said at least one second crank arm element extends cantileveredfrom a respective coupling arm.
 6. Crank arm assembly according to claim4 or 5, wherein said at least one first crank arm element extendscircumferentially without structural interruption between two adjacentcoupling arms.
 7. Crank arm assembly according to claim 6, wherein saidat least one second crank arm element extends from the coupling arm ofsaid two adjacent coupling arms that precedes the other coupling armwith reference to the direction of rotation of said crank arm duringpedaling.
 8. Crank arm assembly according to claim 3, wherein said atleast one front sprocket includes a first front sprocket having a firstdiameter and at least one second front sprocket having a second diameterdifferent from said first diameter, wherein said first front sprocket iscoupled with said crank arm at said at least one first coupling portionand said at least one second front sprocket is coupled with said crankarm at least one second coupling portion different from said at leastone first coupling portion, wherein said at least one second couplingportion is defined in said at least one coupling arm.
 9. Crank armassembly according to claim 3, wherein said crank arm further comprisesan additional coupling portion defined in said first body portion. 10.Crank arm assembly according to claim 9, wherein said first frontsprocket and at least one second front sprocket couple with said crankarm at said additional coupling portion.
 11. Crank arm assemblyaccording to claim 1, comprising a plurality of first crank arm elementsand a plurality of second crank arm elements.
 12. Crank arm assemblyaccording to claim 1, wherein at least some of said at least one firstcrank arm element and at least one second crank arm element extend atleast partially along respective non-radial directions with respect to arotational axis of said crank arm about which the crank arm rotates. 13.Crank arm assembly according to claim 12, wherein at least some of saidat least one first crank arm element and at least one second crank armelement extend at least partially circumferentially.
 14. Crank armassembly according to claim 13, wherein at least some of said at leastone first crank arm element and at least one second crank arm elementextend around said rotational axis of said crank arm along respectivearcs of circumference having an angular extension of less than 360°. 15.Crank arm assembly according to claim 12, wherein said at least onefirst crank arm element and at least one second crank arm element act inabutment on said at least one front sprocket at different angularpositions.
 16. Crank arm assembly according to claim 1, wherein said atleast one first crank arm element and at least one second crank armelement extend from opposite sides with respect to said at least onefirst coupling portion.
 17. Crank arm assembly according to claim 16,wherein said at least one second crank arm element is arranged in aposition that precedes said at least one first coupling portion withreference to the direction of rotation of said crank arm during pedalingand said at least one first crank arm element is arranged in a positionthat follows said at least one first coupling portion with reference tosaid direction of rotation.
 18. Crank arm assembly according to claim 1,wherein said crank arm comprises at least one abutment surface that whenin proper abutment to the at least one front sprocket ensures thecorrect angular positioning of said crank arm with respect to said atleast one front sprocket.
 19. Crank arm assembly according to claim 18,wherein said at least one abutment surface is defined at least partiallyon said at least one second crank arm element.
 20. Crank arm assemblyaccording to claim 1, wherein said at least one front sprocket includesa first front sprocket having a first diameter and at least one secondfront sprocket having a second diameter different from said firstdiameter, wherein said first front sprocket is coupled with said crankarm at said at least one first coupling portion and said at least onesecond front sprocket is coupled with said crank arm at least one secondcoupling portion different from said at least one first couplingportion.
 21. Crank arm assembly according to claim 20, wherein said atleast one first coupling portion is defined at a first circumferencehaving its center at a rotational axis of said crank arm and said atleast one second coupling portion is defined at least one secondcircumference concentric with said first circumference and having adiameter different from that of said first circumference.
 22. Crank armassembly according to claim 21, wherein said at least one first couplingportion is defined along at least one first substantially radialdirection with respect to said rotational axis of the crank arm and saidat least one second coupling portion is defined along at least onesecond substantially radial direction different from said firstsubstantially radial direction.
 23. Crank arm assembly according toclaim 20, comprising at least two first coupling portions arranged at afirst predetermined angular distance one from the other and at least twosecond coupling portions arranged at a second predetermined angulardistance one from the other, said second predetermined angular distancebeing less than said first predetermined angular distance.
 24. Crank armassembly according to claim 1, wherein said crank arm is made fromcomposite material.
 25. Crank arm assembly according to claim 1,comprising at least one first front sprocket element that cooperateswith said at least one first crank arm element and at least one secondfront sprocket element that cooperates with said at least one secondcrank arm element.
 26. Crank arm assembly according to claim 25, whereinat least some of said at least one first crank arm element and at leastone second crank arm element extend at least partially along respectivenon-radial directions with respect to a rotational axis of said crankarm about which the crank arm rotates, wherein at least some of said atleast one first crank arm element and at least one second crank armelement extend at least partially circumferentially wherein said atleast one first front sprocket element has an angular extensionsubstantially equal to that of said at least one first crank armelement.
 27. Crank arm assembly according to claim 25, wherein said atleast one front sprocket comprises an annular element having a radiallyinner surface from which at least one coupling element extends radiallycantilevered towards said crank arm.
 28. Crank arm assembly according toclaim 27, wherein said at least one first front sprocket element and atleast one second front sprocket element are defined in a body portion ofsaid annular element extending radially cantilevered from said radiallyinner surface and comprising said at least one coupling element. 29.Crank arm assembly according to claim 27, wherein said at least onesecond front sprocket element is defined by a respective body portion ofsaid annular element extending radially cantilevered from said radiallyinner surface, said respective body portion not comprising said at leastone coupling element.
 30. Crank arm assembly according to claim 27,wherein said annular element is made from a composite material. 31.Right crank arm for a bicycle, comprising a main body with at least onefirst coupling portion, wherein said main body comprises at least onefirst contact element and at least one second contact element that isformed in a single piece with the first contact element, said at leastone first contact element and said at least one second contact elementbeing angularly offset from one another along a circumferentialdirection and axially offset from one another along a rotational axis ofthe right crank arm, said axial offset creating a gap between said atleast one first element and said at least one second element along therotational axis, the at least one second contact element having acontact surface that faces a corresponding contact surface of the atleast one first contact element.
 32. Crank arm according to claim 31,wherein said at least one first contact element and at least one secondcontact element are formed in a single piece with said main body. 33.Crank arm according to claim 31, wherein said main body comprises aplurality of first contact elements and a plurality of second contactelements.
 34. Crank arm according to claim 31, wherein at least some ofsaid at least one first contact element and at least one second contactelement extend at least partially along respective non-radial directionswith respect to a rotational axis of said crank arm.
 35. Crank armaccording to claim 34, wherein at least some of said at least one firstcontact element and at least one second contact element extend at leastpartially circumferentially.
 36. Crank arm according to claim 35,wherein at least some of said at least one first contact element and atleast one second contact element extend around said rotational axis ofsaid crank arm along respective arcs of circumference having an angularextension of less than 360°.
 37. Crank arm according to claim 36,wherein said respective arcs of circumference have different angularpositions with respect to said rotational axis.
 38. Crank arm accordingto claim 31, wherein said at least one first contact element and atleast one second contact element extend from opposite sides with respectto said at least one first coupling portion.
 39. Crank arm according toclaim 38, wherein said at least one second contact element is arrangedin a position that precedes said at least one first coupling portionwith reference to the direction of rotation of the crank arm duringpedaling and said at least one first contact element is arranged in aposition that follows said at least one first coupling portion withreference to said direction of rotation.
 40. Crank arm according toclaim 31, wherein said main body comprises at least one abutment surfacethat allows the correct angular positioning of said crank arm withrespect to at least one front sprocket.
 41. Crank arm according to claim40, wherein said at least one abutment surface is defined at leastpartially on said at least one second contact element.
 42. Crank armaccording to claim 31, wherein said main body comprises at least onefirst coupling portion at a different radial distance from therotational axis than at least one second coupling portion.
 43. Crank armaccording to claim 42, wherein said at least one first coupling portionis defined at a first circumference having its center at the rotationalaxis of said crank arm and said at least one second coupling portion isdefined at least one second circumference concentric with said firstcircumference and having a diameter different to that of said firstcircumference.
 44. Crank arm according to claim 43, wherein said atleast one first coupling portion is defined along at least one firstsubstantially radial direction with respect to said rotational axis andsaid at least one second coupling portion is defined along at least onesecond substantially radial direction different from said firstsubstantially radial direction.
 45. Crank arm according to claim 42,wherein said main body comprises at least two first coupling portionsarranged at a first predetermined angular distance one from the otherand at least two second coupling portions arranged at a secondpredetermined angular distance one from the other, said secondpredetermined angular distance being shorter than said firstpredetermined angular distance.
 46. Crank arm according to claim 31,wherein said main body comprises a first body portion that couples witha bicycle pedal and a second body portion with at least one arm thatextends substantially radially with respect to a rotational axis of saidcrank arm, wherein said at least one first coupling portion is definedin said at least one coupling arm and said at least one first contactelement and at least one second contact element extend from said atleast one coupling arm along non-radial directions on opposite sideswith respect to said at least one coupling portion.
 47. Crank armaccording to claim 46, wherein said main body comprises a plurality ofcoupling arms and wherein said at least one first contact element and atleast one second contact element extend from at least some of saidcoupling arms.
 48. Crank arm according to claim 47, wherein said atleast one first contact element extends circumferentially withoutstructural interruption between two adjacent coupling arms.
 49. Crankarm according to claim 48, wherein said at least one second contactelement extends from the coupling arm that precedes said at least onecoupling portion with reference to the direction of rotation of saidcrank arm during pedaling.
 50. Crank arm according to claim 46, whereinsaid at least one second contact element extends cantilevered from arespective coupling arm.
 51. Crank arm according to claim 46, whereinsaid main body comprises at least one first coupling portion at adifferent radial distance from the rotational axis than at least onesecond coupling portion, wherein said at least one second couplingportion is defined in said at least one coupling arm.
 52. Crank armaccording to claim 31, wherein said main body is made from light metalmaterial or from composite material.
 53. Front sprocket for a cranksetof a bicycle, comprising an annular element having at least one couplingportion, said annular element comprising at least one first contactelement and at least one second contact element, said at least one firstcontact element and said at least one second contact element beingformed in a single piece with each other, angularly offset from oneanother along a circumferential direction, and axially offset from oneanother along a rotational axis of the annular element.
 54. Frontsprocket according to claim 53, wherein said annular element comprises aplurality of first contact elements and a plurality of second contactelements.
 55. Front sprocket according to claim 53, wherein said atleast one first contact element and at least one second contact elementextend at least partially along respective non-radial directions withrespect to a rotational axis of said front sprocket.
 56. Front sprocketaccording to claim 55, wherein said at least one first contact elementand at least one second contact element extend at least partiallycircumferentially around said rotational axis of said front sprocketalong respective arcs of circumference having an angular extension ofless than 360°.
 57. Front sprocket according to claim 56, wherein saidrespective arcs of circumference have different angular positions withrespect to said rotational axis.
 58. Front sprocket according to any oneof claim 53, wherein said at least one first contact element and atleast one second contact element extend from opposite sides with respectto said at least one coupling portion.
 59. Front sprocket according toclaim 58, wherein said at least one second contact element is arrangedin a position that precedes said at least one coupling portion withreference to the direction of rotation of the front sprocket duringpedaling and said at least one first contact element is arranged in aposition that follows said at least one coupling portion with referenceto said direction of rotation.
 60. Front sprocket according to claim 53,wherein said annular element comprises at least one abutment surfaceadapted to allow the correct angular positioning of said front sprocketwith respect to said crank arm.
 61. Front sprocket according to claim60, wherein said at least one abutment surface is defined at leastpartially in said at least one second contact element.
 62. Frontsprocket according to claim 53, wherein said annular element comprises aradially inner surface from which at least one coupling element withsaid crank arm extends radially, said at least one coupling portionbeing defined in said at least one coupling element.
 63. Front sprocketaccording to claim 62, wherein said at least one first contact elementand at least one second contact element are defined in a body portion ofsaid annular element extending radially cantilevered from said radiallyinner surface and comprising said at least one coupling element. 64.Front sprocket according to claim 62, wherein said at least one secondcontact element is defined by a respective body portion of said annularelement extending radially cantilevered from said radially innersurface, wherein said respective body portion does not include said atleast one coupling element.
 65. Front sprocket according to claim 62,wherein said at least one first contact element extendscircumferentially without structural interruption between two adjacentcoupling elements.
 66. Front sprocket according to claim 63, whereinsaid annular element is made from a composite alloy.
 67. Right crank armassembly for a bicycle, comprising a right crank arm and at least onefront sprocket coupled with said crank arm, wherein said right armassembly comprises at least one first crank arm element that contactssaid at least one front sprocket and that extends along a non-radialdirection with respect to a rotational axis of said crank arm, and atleast one second crank arm element formed in a single piece with said atleast one first crank arm element and angularly offset from said atleast one first crank arm element along a circumferential direction,wherein said at least one front sprocket has an inner side that facestowards a frame of said bicycle and an outer side opposite said innerside, and said at least one first crank arm element contacts said atleast one front sprocket on said outer side, and said at least onesecond crank arm element contacts said at least one second crank armelement on said inner side.
 68. Crank arm assembly according to claim67, wherein said crank arm comprises at least one coupling arm with saidat least one front sprocket extending along a substantially radialdirection and wherein said at least one crank arm element extends fromsaid at least one coupling arm.
 69. Crank arm assembly according toclaim 68, wherein said crank arm comprises a plurality of coupling armsand wherein said at least one crank arm element extends from at leastsome of said coupling arms.
 70. Crank arm assembly according to claim69, wherein said at least one crank arm element extendscircumferentially without structural interruption between two adjacentcoupling arms.
 71. Crank arm assembly according to any one of claims 67to 69, wherein said at least one crank arm element extends at leastpartially circumferentially around said rotational axis of said crankarm along an arc of circumference having a predetermined angularextension.
 72. Crank arm assembly according to claim 71, wherein saidangular extension is less than 360° and greater than or equal to 15°.73. Crank arm assembly according to claim 72, wherein said angularextension is between 15° and 100°.
 74. Crank arm assembly according toclaim 73, wherein said angular extension is between 30° and 75°. 75.Crank arm assembly according to claim 72, wherein said at least onecrank arm element extends cantilevered from said at least one couplingarm.
 76. Crank arm assembly according to claim 67, wherein said crankarm is made from a composite material.
 77. Crank arm assembly accordingto claim 67, comprising at least one front sprocket element thatcooperates with said at least one crank arm element, wherein said atleast one front sprocket element has an angular extension substantiallyequal to that of said at least one crank arm element.
 78. Crank armassembly according to claim 77, wherein said at least one front sprocketcomprises an annular element having a radially inner surface from whichat least one coupling element with said crank arm extends radiallycantilevered.
 79. Crank arm assembly according to claim 78, wherein saidannular element is made from a composite material.
 80. Right crank armfor a bicycle, comprising a main body adapted to be coupled with atleast one front sprocket of a crankset of a bicycle, said at least onefront sprocket has an inner side that faces towards a frame of saidbicycle and an outer side that faces away from said frame, wherein saidmain body comprises at least one first contact element that extendsalong a non-radial direction with respect to a rotational axis of saidcrank arm and at least one second contact element formed in a singlepiece with said at least one first contact element and angularly offsetfrom said at least one first contact element along a circumferentialdirection, wherein said at least one first contact element contacts saidat least one front sprocket on said outer side, and said at least onesecond contact element contacts said at least one front sprocket on saidinner side.
 81. Crank arm according to claim 80, wherein said main bodycomprises at least one coupling arm with said at least one frontsprocket extending along a substantially radial direction and whereinsaid at least one contact element extends from said at least onecoupling arm.
 82. Crank arm according to claim 81, wherein said mainbody comprises a plurality of coupling arms and wherein said at leastone contact element extends from at least some of said coupling arms.83. Crank arm according to claim 82, wherein said at least one contactelement extends circumferentially without structural interruptionbetween two adjacent coupling arms.
 84. Crank arm according to claim 80,wherein said at least one contact element extends at least partiallycircumferentially around said rotational axis along an arc ofcircumference having a predetermined angular extension.
 85. Crank armaccording to claim 84, wherein said angular extension is less than 360°and greater than or equal to 15°.
 86. Crank arm according to claim 85,wherein said angular extension is between 15° and 100°.
 87. Crank armaccording to claim 86, wherein said angular extension is between 30° and75°.
 88. Crank arm according to claim 80, wherein said main body is madefrom a composite material.
 89. Front sprocket for a crankset of abicycle, comprising an annular element adapted to be coupled with aright crank arm of a bicycle, wherein said annular element comprises atleast one first contact element that contacts a side of said right crankarm and extends along a non-radial direction with respect to arotational axis of said front sprocket, and at least one second contactelement that is formed in a single piece with said at least one firstcontact element and contacts an opposing side of said right crank arm,said at least one first contact element and at least one second contactelement being angularly offset from one another along a circumferentialdirection.
 90. Front sprocket according to claim 89, wherein saidannular element comprises at least one coupling element and wherein saidat least one contact element extends from said at least one couplingelement.
 91. Front sprocket according to claim 89, wherein said at leastone coupling element extends radially cantilevered from a radially innersurface of said annular element.
 92. Front sprocket according to claim89, wherein said annular element is made from a composite material. 93.Right crank arm assembly for a bicycle, comprising a right crank arm andat least one front sprocket coupled with said crank arm at least onefirst coupling portion of said crank arm, wherein said at least onefront sprocket has an inner side intended, in use, to face towards aframe of the bicycle and an outer side opposite said inner side, andwherein said crank arm comprises at least one first crank arm elementwhich contacts one of said sides of the at least one front sprocket, atleast one second crank arm element which contacts the other of saidsides of the at least one front sprocket, and a main body, said at leastone first crank arm element and at least one second crank arm elementbeing angularly offset from one another along a circumferentialdirection, and being formed in a single piece with each other and withsaid main body.
 94. Right crank arm for a bicycle, comprising a mainbody with at least one first coupling portion, wherein said main bodycomprises at least one first contact element and at least one secondcontact element, said at least one first contact element and said atleast one second contact element being angularly offset from one anotheralong a circumferential direction and axially offset from one anotheralong a rotational axis of the right crank arm, said axial offsetcreating a gap between said at least one first element and said at leastone second element along this rotational axis, and wherein said at leastone first contact element and at least one second contact element areformed in a single piece with each other and with said main body. 95.Right crank arm assembly for a bicycle, comprising a right crank arm andat least one front sprocket coupled with said crank arm, wherein saidright arm assembly comprises at least one first crank arm element whichcontacts said at least one front sprocket and that extends along anon-radial direction with respect to a rotational axis of said crankarm, and at least one second crank arm element that is formed in asingle piece with said at least one first crank arm element andangularly offset from said at least one first crank arm element along acircumferential direction, said crank arm comprising a main body andsaid at least one first crank arm element being formed in a single piecewith said main body.